Thermal processing is commonly practiced in the semiconductor industry. Semiconductor substrates are subjected to thermal processing in the context of many transformations, including doping, activation, and annealing of gate source, drain, and channel structures, siliciding, crystallization, oxidation, and the like. Over the years, techniques of thermal processing have progressed from simple furnace baking to various forms of increasingly rapid thermal processing such as RTP, spike annealing, and laser annealing.
Conventional laser annealing processes use laser emitters that may be semiconductor or solid state lasers with optics that focus, defocus, or variously image the laser light into a desired shape. A common approach is to image the laser light into a line or thin rectangle image. The laser light is scanned across a substrate (or the substrate moved beneath the laser light) to process the entire surface of the substrate.
As device geometry continues to decline, semiconductor manufacturing processes such as thermal processing are challenged to develop increased precision. In many instances, pulsed laser processes are being explored to reduce overall thermal budget and reduce depth and duration of energy exposure at the substrate. Challenges remain, however, in creating laser pulses having a temporal shape that affords the desired processing performance, with the uniformity needed for uniform processing across the surface of a substrate. Thus, there is a continuing need for new apparatus and methods for thermal processing of semiconductor substrates.